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- Can dairy slurry application to stubble, without Incorporation into the soil, be sustainable?Publication . Silva, Arejacy; Carvalho, Mario; Coutinho, João; Vasconcelos, Ernesto; Fangueiro, DavidIn many countries, livestock slurry must be injected or incorporated into the soil to reduce nitrogen losses. However, when the injection is not feasible, farmers adopting conservation practices discard the use of slurry as fertilizer. New approaches related to slurry treatment or application management can stimulate the use of slurry in conservation agriculture (CA). This study aimed to evaluate the agronomic effects of some new management strategies to use dairy slurry for fertilization of ryegrass grown on stubble-covered soil, using as reference standard practices (slurry injection and mineral fertilizer application). The following treatments were considered: (i) bare soil: control (CB), mineral fertilizer (MB), injection (IN); (ii) stubble: control (CS), acidified dairy slurry (ADS), raw dairy slurry (RDS), irrigation following RDS (IR), mineral fertilizer (MS), RDS placed under the stubble (US), raw slurry applied 16 days after sowing (RDS T16). Effects on ryegrass yield, apparent nutrient recovery (ANR) and soil chemical properties were assessed. ADS reached 94% equivalence to MS and performed similarly to IN for productivity, ANR and soil parameters showing to be a sustainable alternative to replace mineral nitrogen and a potential solution to enable dairy slurry application in CA without injection or incorporation into the soil.
- Dairy Slurry Application to Stubble-Covered Soil: A Study on Sustainable Alternatives to Minimize Gaseous EmissionsPublication . Silva, Arejacy António; Carvalho, Mário; Coutinho, João; Vasconcelos, Ernesto; Fangueiro, DavidThe development of sustainable application practices, which do not demand incorporation into the soil, is necessary to encourage slurry use in conservation agriculture (CA). Incorporation is the most common practice to reduce nitrogen losses from the applied slurry. However, in CA, soil disturbance must be avoided. Two experiments were conducted to evaluate strategies to reduce gaseous emissions from dairy slurry applied to stubble-covered soil without incorporation. We evaluated (1) effects on ammonia (NH3) emissions of pretreatment by acidification (ADS), irrigation (IR) and placement under the stubble (US); and (2) effects of ADS, IR, US and delayed fertilization (RDS T16) on greenhouse gases (GHG). The results of the evaluated strategies were compared to raw slurry (RDS) and ammonium sulphate (MS). Additionally, in experiment 2, the results were compared to ammonium sulphate (MB) and slurry injection (IN), both in bare soil. ADS, US and IR decreased NH3 emissions by 66%, 60% and 32.5%, respectively, with total N emissions NH3 emissions accounting for more than 79% of N losses in slurry-based treatments. Late application reduced N2O emissions by 48%. GHG emissions from ADS, US and IR were similar to those from MS, MB and IN. ADS, US and IR are the most suitable strategies for slurry application in CA